1. Field of the Invention
The present invention relates to a numerical control device for performing a control axis switch, and more particularly, to a numerical control device which has a configuration in which a single drive unit is provided for groups of a plurality control object units and a plurality of control axis units and the drive unit is connected thereto by a control axis switch unit as necessary, and enables the connection even in a structure in which the drive unit needs to be connected to each of the control object units at a specific position.
2. Description of the Related Art
When a plurality of control object parts are included in a machine tool, in many cases, each of the control object parts is driven by its dedicated drive source. In this case, there is a problem in that the machine weight is increased by the number of control objects and this causes an increase in cost.
In order to solve this problem, as the related art, a numerical control device in which a single drive unit is provided for groups of a plurality control object units and a plurality of control axis units and the single drive unit is connected to the desired control object unit and the control axis unit by a control axis switch unit as necessary is suggested in JP 09-311706 A.
In the numerical control device described in JP 09-311706 A, control is performed by changing the axis position of a servo motor at the time of reconnection to the control object unit to an axis position at the time of previous separation. Therefore, there is a problem in that connection between the servo motor and each of the control object units is limited to a structure in which connection can be achieved at an arbitrary axis position.
In addition, in the numerical control device described in JP 09-311706 A, when a control object is operated while the control object is not connected to an axis drive motor, a problem that a shift is generated between axis position data stored in each of axis control units and an actual position of a corresponding control object unit, cannot be solved.